Packet radio telephone services

摘要

A method of synchronising radio signal transmission slots at a mobile station to radio signal reception slots at a base station subsystem to account for a propagation delay between the mobile station and the base station subsystem. The method is applicable to a GPRS packet switched cellular telephone network in which a downlink channel is defined for transmitting user data from the base station subsystem to the mobile station and an uplink channel is defined for transmitting user data from the mobile station to the base station subsystem. These channels comprise dynamically allocated time slots in a time division multiple access frame. An updated timing advance value indicative of the radio propagation delay between the mobile station and the base station subsystem at a given time is calculated at the base station once every 8 multiframes. The timing advance value is identified to the mobile station by a timing advance index previously allocated to the mobile station. The mobile station uses the timing advance value to advance transmission slots at the mobile station for both the uplink and downlink channels so that transmitted data is received at the base station subsystem in the allocated base station subsystem reception slots.